c array of pointers

Question

I've been trying to create a function that splits a string and return a pointer to the first element of the array. It compiles with no error but when i run the program it crashes. Here is my code. Any help on how to fix this. Thanks.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define split_count(a) a

int count(char *str, char *sub) {
    int sublen = strlen(sub);
    int templen = 0;
    int count = 0;

    if (sublen > strlen(str))
        return 0;

    int i, j;
    for (i = 0; i < strlen(str); i++) {
        if (*(str + i) == *sub) {
            templen = 1;
            for (j = 1; j < sublen; j++) {
                if (*(str + i + j) == *(sub + j)) {
                    templen += 1;
                }
            }

            if (templen == sublen) {
                count += 1;
            }

            templen = 0;
        }
    }

    return count;
}

char * split(char *str, char *sep, int maxsplit) {
    if (!count(str, sep))
        return NULL;

    char *arr[split_count(count(str, sep)) + 1];

    int i, j;
    int templen = 0;

    int stop = 0;

    int counter = 0;

    for (i = 0; i < strlen(str); i++) {
        if (*(str + i) == *sep) {
            templen = 1;

            for (j = 1; j < strlen(sep); j++) {
                if (*(str + i + j) == *(sep + j)) {
                    templen += 1;
                }

                if (templen == strlen(sep)) {
                    arr[counter] = (char*)malloc(sizeof(char) * strlen(str));

                    strcpy(arr[counter], "");

                    int k;
                    for (k = stop; k < i; k++) {
                        *(arr[counter] + strlen(arr[counter])) = *(str + k);
                        *(arr[counter] + strlen(arr[counter])) = '\0';
                    }

                    stop = i + strlen(sep);

                    counter++;
                }
            }
        }
    }

    return arr[0];
}

int main() {
    char *before = "This is a house isisis is";

    printf("%s\n", split(before, "is", 1));

    return 0;
}

Answer 1

In addition to Acme's answer that you may not modify a string literal:

Looks like your looping through str, increasing i up to i < strlen(str), however, below that you go to str+i+j. What happens when j is like 10 and you are at the the very end of str? You most likely end up going outside of the memory are for str resulting in a segmentation fault.

I recommend looking through string.h which you already include. There are functions for doing this in a much safer way.

Answer 2

This

char *before = "This is a house isisis is";

is a pointer to string literal "This is a house isisis is" - modifying it will crash the program.

Use this:

char before[50] = "This is a house isisis is";

Also your split function has an infinite loop.